1. Field of the Invention
The invention relates to a variable resistance device; in particular, the invention relates to a variable resistance device that makes the assembling easier and enhances its quality.
2. Description of the Related Art
Variable resistance devices find many uses in electrical equipment. One common use of variable resistance devices is used to control voltage in, for example, flyback transformers.
When used in a flyback transformer, a variable resistance device must meet a number of requirements. The foremost requirement is size. This poses a problem for variable resistance devices that typically rely on electromechanical structures to provide variable resistance.
Known variable resistance devices also are typically constructed of a relatively large number of small parts, increasing the difficulty of assembly and, correspondingly, the cost of the devices. In addition, the reliability is impaired because of the likelihood that each of the many parts presents an opportunity for failure in the device.
One example of a known variable resistance device is shown in FIG. 1. Such variable resistance device 10 is consisted of a substrate 11 and a rotor 12. A resistive region 111 is formed on the substrate 11. The resistive region 111 is consisted of a central part 1111 and a semi-circular path 1112. A distance X1 is maintained as a safe gap between the central part 1111 and the semi-circular path 1112. The central part 1111 is electrically connected to an external circuit (not shown). A spring 121 is disposed at the bottom of the rotor 12. The spring 121 has a first end 1211 and a second end 1212.
The first end 1211 of the spring 121 is in contact with the central part 1111 of the resistive region 111. The second end 1212 of the spring 121 is in contact with the semi-circular path 1112 of the resistive region 111. The second end 1212 is movable along the semi-circular path 1112.
Therefore, users can move the second end 1212 along the semi-circular path 1112 by rotating the rotor 12 to change the resistance.
The disadvantage of the variable resistance device 10 is that its size has a minimum limit. Specifically, since two ends of the spring 121 are on the same plane, in view of the safe gap X1, the size of the substrate 11 has a minimum limit.
The other example of a known variable resistance device is shown in FIG. 2. Such variable resistance device 20 is also consisted of a substrate 21 and a rotor 22. A resistive region 211 is formed on the substrate 21. The resistive region 211 comprises a semi-circular path. A point C1 is used as a center of the semi-circular path. A distance Y2 is maintained as a safe gap between the point C1 and the semi-circular path. The rotor 22 is provided with a rod 221 and an elastic strip 222 at its bottom. The elastic strip 222 has a first end 2221 and a second end 2222. The rod 221 abuts the point C1 of the substrate 21. The first end 2221 is movable along the resistive region 211, and the second end 2222 is electrically connected to an external circuit (not shown). Therefore, users can move the first end 2221 along the semi-circular path by rotating the rotor 22 to change the resistance.
As shown in FIG. 2, the first end 2221 of the variable resistance device 20 extends outwardly from the bottom of the rotor 22 in an inclined angle. Hence, comparing with the safe gap X1 as shown in FIG. 1, the safe gap Y2 can be reduced. As a result, the size of the substrate 21 can be decreased.
However, the disadvantages of the variable resistance device 20 are that its elastic strip 222 is easily deformed, it is hard to assemble, and it cannot be assembled repeatedly.
In view of the disadvantages of the aforementioned conventional variable resistance device, the invention provides a variable resistance device that can make the assembly easier and enhances its quality.
Accordingly, the variable resistance device of the invention comprises a substrate and a rotor. A resistive region is formed on the substrate. The rotor is disposed on the substrate, after which it is rotatable. The rotor comprises a first contact member, a mount, a rotating member and a second contact member. The first contact member has a first end and a second end, wherein the first end abuts the resistive region in an elastic manner. The mount is used for receiving the first contact member. The rotating member engages the mount. The second contact member, disposed between the mount and the rotating member, abuts the second end of the first contact member in a movable manner.
Furthermore, the mount has a first through hole and a receiving portion; therefore, the rotating member passes through the first through hole to engage the mount, and the receiving portion is used for receiving the first contact member.
Furthermore, the receiving portion is a second through hole.
Furthermore, the first contact member comprises a rivet, a spring and a ball. The rivet abuts the resistive region. The spring, surrounding the rivet, is disposed inside the second through hole and abutting the rivet in one end. The ball abuts the second contact member and the other end of the spring.
Furthermore, the first contact member comprises a spring, a first ball and a second ball. The spring is disposed inside the second through hole. The first ball is disposed between the second contact member and one end of the spring. The second ball is disposed between the substrate and the other end of the spring.
Furthermore, the first contact member comprises a rivet and a spring. The rivet abuts the resistive region in one end. The spring, surrounding the rivet, is disposed inside the second through hole.
Furthermore, the second contact member has a hollow portion for the rotating member passing through.
Furthermore, the variable resistance device further comprises a housing. The housing has a first portion for combining with the substrate and a second portion for combining with the rotor.
Furthermore, a variable resistance device of the invention comprises a substrate and a rotor. A resistive region is formed on the substrate. The rotor is rotatablly disposed on the substrate and comprises a first contact member, a mount, a rotating member, a second contact member and a cushion member. The first contact member has a first end and a second end. The first end abuts the resistive region. The mount is used for receiving the first contact member. The rotating member engages the mount. The second contact member, disposed between the mount and the rotating member, abuts the second end of the first contact member in a movable manner. The cushion member, disposed between the second contact member and the rotating member, is used for cushioning the contact between the first contact member and the resistive region.
Furthermore, a variable resistance device of the invention comprises a substrate and a rotor. A resistive region is formed on the substrate. The rotor is disposed on the substrate, after which it can rotate, and comprises a first contact member, a mount, a rotating member and a conducting interface. The first contact member has a first end and a second end. The first end abuts the resistive region. The mount is used for receiving the first contact member. The rotating member engages the mount, and the rotating member abuts the mount. The conducting interface is formed on a surface, abuts the mount, of the rotating member. The conducting interface abuts the second end of the first contact member in a movable manner.